Path: utzoo!attcan!uunet!lll-winken!lll-crg.llnl.gov!bowles
From: bowles@lll-crg.llnl.gov (Jeff Bowles)
Newsgroups: comp.unix.microport
Subject: Re: Physical memory access with SystemV/AT
Message-ID: <8565@lll-winken.llnl.gov>
Date: 13 Jun 88 13:48:50 GMT
References: <185@focsys.UUCP> <1019@sdcc12.ucsd.EDU>
Sender: usenet@lll-winken.llnl.gov
Reply-To: bowles@lll-crg.llnl.gov.UUCP (Jeff Bowles)
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Organization: Lawrence Livermore National Laboratory
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In article <1019@sdcc12.ucsd.EDU> mp1@sdcc12.ucsd.EDU (Leroy Dorman) writes:
>In article <185@focsys.UUCP>, larry@focsys.UUCP (Larry Williamson) writes:
>> I would like to do something like:
>> 	shmcreate 0x800000 800000 1048560
>> to create a 1Meg shared memory segment at the 8meg address location.
>
>Unless Microport put in a peek/poke-style function in to V/AT,
>(the Rel 1.0 from At&t didn't have one)
>there's no way to access physical memory from u-space...

If you mean dereference a pointer and you're changing a character on the
video screen, no, there's no portable way to do it. I am running Bell Tech
SVR3, and the only choice *I* have is to open "/dev/mem" and lseek(2) to
the location of the video buffer and write(2) out the places I want to change.

But it DOES work, folks, albeit slowly (1-2 milliseconds to update the screen
via one write(2) system call).

More info, send me mail. It's not that hard, but certainly clumsy.

	Jeff Bowles